Electrodynamic sound reproducer



Oct. 24, 1950 H. c. WILLSON 2,526,836

ELECTRODYNAMIC souun REPRODUCER Filed Dec. 5, 1945 F/GZ /n 1 9/7 for 9 Harry 6. Wi/ISOI'I Patented Oct. 24, 1950 UNITED STATES PATENT OFFICE ELECTRODYNAMIC SOUND nErRoDUcER Harry Claude Willson', Wolverhampton, England,

Application December 3, 1945, Serial No. 632,531

. 1 In Great Britain December 8, 1944 This invention relates to electro-dynamic reproducers or loud-speakin telephones, that is to say, loud speaking telephones of the moving coil type, either furnished with a permanent magnet system or a current energised magnet system. The invention is more particularly concerned with the centering of the moving coil in such instruments and the arrangements for leading in current to the moving coils.

The use of centering members in the form of corrugated discs or spiders formed of compressed paper or linen or of deposited pulp, is well-known. Their use, however, has hitherto been associated with certain disadvantages, particularly with regard to the provision of suitable means for bringing substantial leads from the moving voice coil to a fixed anchoring. The usual practice has been to secure eyelets in the cone diaphragm itself, the incoming leads and the wires from the moving coil being soldered together at these eyelets. The provision of rivets and tags at isolated points on the diaphragm clearly is liable to affect its normal modes of vibration, and in addition, the voice coil leads taken to a fixed point impose inertia loads on the diaphragm which also tend to produce undesired effects in the reproduction.

The present invention seeks to overcome these drawbacks by incorporating the leads to the moving coil in the centerin member itself, soas to form an actual part of that member.

To this end, according to the invention, the centering member or spider is composed of two layers of suitably impregnated material pressed together to form the centering member and sandwiched between them are leads of wire or thin strip. In a convenient form, these leads lie along a diameter coming towards the centre from opposite sides and their inner ends appearing at the central aperture in the centering member are connected, as for example, by soldering to the wires from the moving coil. Alternatively, the leads may run spirally, tangentially or radially on the same side of a diameter, to the central circular aperture. The outer stationary ends of the sandwiched leads are connected to members of any suitable type, by means of which the audio-frequency currents are introduced to the voice coil itself. The two layers obviously need not be of the same thickness, nor necessarily of the same material.

In order that the invention may be clearly understood and readily carried into effect, an example of the novel form of construction will now be described with reference to the accompanying drawings in which:

v 4 Claims. (Cl. 179-115.5)

Figure 1 is a front elevation of the completed centering disc; and

Figure 2 is a section on the line 11-11 in Fig ure 1, showing the parts somewhat separated.

In this example, the centering disc or spider is formed of two layers of fabric a, b which have been impregnated with thermo-plastic or thermosetting resin while in the fiat condition, and then have been pressed in dies or in a mould to impart to them the corrugations c and to set the resin. The amount of resin used may be sufficientto render the discs at, b impervious to air or less may be used so that air can pass through the discs. Sandwiched between the two discs at, b are two thin strips 11, e of beryllium-copper alloy or copper or other suitable conducting material to form the leads connected to the two ends of the speech coil at their inner ends. The leads d, e are connected at their outer ends to terminals on the loud-speaker chassis toreceive the input currents.

Two additional strips f, g of the same crosssection as the strips d, e are inserted between the discs a, b at equal angles to the leads d, e. These strips f, g take no part in the conduction of current but are provided to equalise the resistance to bending of the centering spider at all angular positions, and to equalise the displacement of the whole of the inner portion of the diaphragm of the loud-speaker.

The invention is thus shown as applied to corrugated centering members but may also be applied to a spider of the well-known type of circular disc form, stamped with slots in the form of arcs or part spirals, provided for the purpose of increasing flexibility or resiliency of the spider. In such a case a piece of metal foil of sufficient area to permit a continuous strip being left is placed across the centering member, between the two layers. This foil is separated into two opposite parts when the central aperture is stamped, and when the arc-shaped or spiral slots are stamped the configuration of the foil is such that on each side there is a continuous piece of the foil left to provide a continuous path for the edge, and a pair of thin lead-in conductors for said moving coil embedded in said structure between said two disks, the central aperture of said unitary annular structure being of substantially the same diameter as the diameter of said coil, and said lead-in conductors being embedded in said structure from said aperture to the peripheral edge of said disks.

2. A centering member and lead-in structure for the moving coil of an electro-dynamic sound reproducer comprising, two disks of thin flexible fabric material having central apertures formed therein and being impregnated with cement and bonded together by said cement in face-to-face relation to form a unitary annular structure of uniform flexibility from its inner to its "outer edge, and a pair of thin metallic strips forming lead-in conductors for said moving coil embedded in said structure between said two disks, and arranged along radii of said annular structure, the central aperture of said unitary annular structure being of substantially the same diameter as the diameter of said coil, and said leadin conductors being embedded in said structure from said aperture to the peripheral edge of said disks.

3. A centering member and lead-in structure for the moving coil of an electro-dynamic sound reproducer comprising, two disks of thin flexible fabric material having central apertures formed therein and being impregnated with cement and bonded together by said cement in face-to-face relation to form a unitary annular structure of uniform flexibility from its inner to its outer edge, and a pair of thin metallic strips forming leadin conductors for said moving coil embedded in said structure between said two disks and arranged along radii of said annular structure, the central aperture of said unitary annular structure being of substantially the same diameter as the diameter of said coil, and two additional metallic strips of the same cross-section as said lead-in conductors and embedded in said annular structure between said fabric disks, at equal angles to said lead-in conductors, for the purpose of equalizing 'the resistance to bending of the centering member at different angular positions thereof.

4'. A centering member according to claim 1 wherein said two disks forming said unitary annular structure are formed with concentric corrugations and said embedded lead-in conductors follow said corrugations. v

HARRY CLAUDE WILLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,794,831 Carus0 Mar. 3, 1931 1,831,235 Farrow -11 Nov. 10, 1931 1,855,600 Clarke Apr. 26, 1932 1,907,687 Van Lis 1 May 9, 1933 2,221,068 Alons Nov. 12. 1940 

